1. Field of the Invention
The present invention relates to a device that drives a cooling fan.
2. Description of the Related Art
In hydraulically driven machinery such as construction machinery, an engine drives a hydraulic pump, and pressure oil discharged from the hydraulic pump is supplied to hydraulic actuators such as hydraulic cylinders via control valves. In this way, the machinery is able to operate.
The engine and the pressure oil have to be cooled.
Cooling devices that use water-cooling techniques are principally used for the cooling of engines. Specifically, cooling is performed by circulating a coolant cooling water through a water jacket provided in the engine main body. Coolant that has been heated up inside the water jacket is guided to a radiator where it is cooled down, and the cooled coolant is then returned to the water jacket.
The pressure oil is cooled by guiding the oil through an oil cooler. Energy losses inside the hydraulic circuit are conducted to the pressure oil in the form of heat. Like the coolant, the pressure oil is guided to an oil cooler where it is cooled down, and the cooled pressure oil is then returned to the hydraulic circuit.
The radiator and oil cooler are both cooled by a flow of air generated by a cooling fan. In most cases the oil cooler and radiator are installed sequentially along the passage of the airflow generated by the cooling fan. This specific arrangement is normally considered to be efficient for cooling purposes.
This cooling fan is attached to the drive shaft of the engine. The rotation speed of the cooling fan thus depends on the rotation speed of the engine.
There is a demand for freedom of layout of the engine and cooling fan as a means of addressing problems associated with the space available for their installation. Consequently, a measure has been adopted whereby the cooling fan is made independent of the engine. This approach is disclosed in Japanese Patent Application Laid-open No. 6-58145.
This publication describes an invention wherein a variable capacity hydraulic pump for driving the fan and a fixed capacity hydraulic motor for driving the fan are installed separately from the engine, and the cooling fan is driven by supplying the pressure oil discharged from the variable capacity hydraulic pump for driving the fan to the fixed capacity hydraulic motor for driving the fan.
In this case, a solenoid control valve for exclusive fan drive use is provided which controls the swash plate of the variable capacity hydraulic pump. Then, according to which temperature range the coolant temperature falls into from among three stages of temperatures, a control signal is applied to the solenoid of the abovementioned solenoid control valve, and the rotation speed of the cooling fan is thereby switched between three stages.
A technique disclosed in Japanese Unexamined Patent Application JP-A No. S63-124820 has also been employed.
This publication describes an invention wherein a fixed capacity hydraulic pump for driving the fan and a fixed capacity hydraulic motor for driving the fan are provided separately from the engine, and the cooling fan is driven by supplying the pressure oil discharged from the fixed capacity hydraulic pump for driving the fan to the fixed capacity hydraulic motor for driving the fan via a flow rate control valve.
In this case, the fixed capacity hydraulic pump discharges pressure oil at a flow rate corresponding to the magnitude of the engine rotation speed. Then, by controlling the aperture of the flow rate control valve, the flow rate of the pressure oil supplied from the fixed capacity hydraulic pump to the fixed capacity hydraulic motor is controlled, and the rotation speed of the cooling fan is controlled.
To reduce the noise produced by construction machinery, there has also been a demand in recent years for reducing the fan rotation speed and reducing energy losses.
In all the inventions described in the abovementioned publications, the cooling fan is driven with a hydraulic pump as a drive source that is separate from the engine. This has the effect of increasing the freedom in the arrangement of the cooling fan radiator, oil cooler and other equipment, and makes it possible to shield the engine while cooling it with the cooling fan at the same time. However, these inventions have suffered from the following problems.
Specifically, the invention of the abovementioned Japanese Patent Application Laid-open No. 6-58145 only controls the rotation speed of the cooling fan in three stages according to which of the three stages of temperature regions the coolant temperature belongs to. As a result, the coolant is not necessarily cooled with optimal energy efficiency. The noise generated by the cooling fan itself may also become greater then necessary. Specifically, since the rotation speed of the cooling fan is varied in three stages, there will be cases when the cooling fan is rotated at a greater speed than is necessary and sufficient for cooling. The noise produced by the cooling fan also increases by an amount corresponding to this increase in rotation speed.
Also, the invention of the abovementioned Japanese Patent Application Laid-open No. 63-124820 only controls the pressure oil supplied to the fixed capacity hydraulic motor from the fixed capacity hydraulic pump by controlling the aperture of the flow rate control valve. Consequently, energy losses occur due to the recirculation of pressure oil from the flow rate control valve to the tank.
Specifically, since the flow rate of pressure oil discharged from the fixed capacity hydraulic pump increases correspondingly with increases in the engine rotation speed, a large amount of pressure oil is restricted by the flow control valve and recirculated to the tank when the engine rotation speed is large. Thus, when the engine rotation speed is large, the amount recirculated to the tank increases and energy losses occur.
Therefore, the present invention is directed at solving the problem of making it possible to drive a cooling fan with a hydraulic source in the most energy efficient way, and at enabling the noise to be controlled to a minimum.
Therefore, the first invention of the present invention is a cooling fan drive control device equipped with a hydraulic pump 2 driven by a drive source 1, a cooling fan 8 which cools cooling water of the drive source 1, and a hydraulic motor 7 which is operated by pressure oil discharged from the hydraulic pump 2 and causes the cooling fan 8 to rotate,
wherein it also comprises:
a cooling water temperature sensing means 23 which senses a temperature of the cooling water,
a target fan rotation speed setting means 50 which sets a target fan rotation speed corresponding to the temperature sensed by the cooling water temperature sensing means 23, and
a capacity control means 47, 40 which controls a capacity 2a of the hydraulic pump 2 or the hydraulic motor 7 according to a difference between a fan rotation speed of the cooling fan 8 and the target fan rotation speed set by the target fan rotation speed setting means 50.
The first invention is described with reference to FIGS. 1(a) and 1(b) and FIG. 2.
With the first invention, a target fan rotation speed FANRPM is set according to the temperature Tc sensed by the cooling water temperature sensing means 23. The capacity 2a of the hydraulic pump 2 or hydraulic motor 7 is then controlled by the capacity control means controller 47, EPC valve 40 so that the fan rotation speed N of the cooling fan 8 becomes the abovementioned target fan rotation speed FANRPM.
With the first invention, a target fan rotation speed FANRPM that is necessary and sufficient for cooling is determined from the current temperature Tc of the cooling water, and the cooling fan 8 is rotated at this target fan rotation speed FANRPM.
Consequently, the cooling water is cooled with optimal energy efficiency. Also, the noise generated by the cooling fan itself does not become greater than is necessary. That is, since the rotation speed of the cooling fan is varied without stages to the rotation speed that is necessary and sufficient for cooling, the cooling fan does not rotate at a rotation speed greater than is necessary and sufficient for cooling. Consequently the rotation speed does not increase above the rotation speed that is necessary and sufficient for cooling, and energy losses do not occur. Also, no noise is generated by the cooling fan. And since there is no recirculation to the tank due to limiting the flow rate with a flow rate control valve, there are also no energy losses due to excessive flow rates.
Thus with the first invention, when driving a cooling fan with a hydraulic source, it is possible to drive it with optimal energy efficiency and to control noise to a minimum.
The second invention is a cooling fan drive control device which comprises a hydraulic pump 2 driven by a drive source 1, a cooling fan 8 which cools pressure oil of equipment 43 operated by the drive source 1, and a hydraulic motor 7 which is operated by pressure oil discharged from the hydraulic pump 2 and causes the cooling fan 8 to rotate,
wherein it also comprises:
a pressure oil temperature sensing means 45 which senses a temperature of the pressure oil,
a target fan rotation speed setting means 50 which sets a target fan rotation speed corresponding to the temperature sensed by the pressure oil temperature sensing means 45, and
a capacity control means 47, 40 which controls a capacity of the hydraulic pump 2 or the hydraulic motor 7 according to a difference between a fan rotation speed of the cooling fan 8 and the target fan rotation speed set by the target fan rotation speed setting means 50.
The second invention is arrived at by substituting the cooling fan 8 which cools the cooling water in the first invention with a cooling fan 8 which cools the pressure oil.
With the second invention, similar advantages are obtained as with the first invention.
The third invention is a cooling fan drive control device which comprises a hydraulic pump 2 driven by a drive source 1, a cooling fan 8 which cools cooling water of the drive source 1 and also cools pressure oil of equipment 43 operated by the drive source 1, and a hydraulic motor 7 which is operated by pressure oil discharged from the hydraulic pump 2 and causes the cooling fan 8 to rotate,
wherein it also comprises:
a cooling water temperature sensing means 23 which senses a temperature of the cooling water,
a pressure oil temperature sensing means 45 which senses a temperature of the pressure oil,
a target fan rotation speed setting means 50 which sets a target fan rotation speed to a first target fan rotation speed corresponding to the cooling water temperature sensed by the cooling water temperature sensing means 23 or to a second target fan rotation speed corresponding to the pressure oil temperature sensed by the pressure oil temperature sensing means 45, whichever is the larger, and
a capacity control means 47, 40 which controls a capacity 2a of the hydraulic pump 2 or the hydraulic motor 7 according to a difference between a fan rotation speed of the cooling fan 8 and the target fan rotation speed set by the target fan rotation speed setting means 50.
The third invention is described with reference to FIGS. 1(a) and 1(b) and FIG. 2.
With the third invention, the target fan rotation speed FANRPM is set to a first target fan rotation speed corresponding to the cooling water temperature Tc sensed by the cooling water temperature sensing means 23 or to a second target fan rotation speed corresponding to the pressure oil temperature Ttc sensed by the pressure oil temperature sensing means 45, whichever is the larger. The capacity control means (controller 47, EPC valve 40) then controls the capacity 2a of the hydraulic pump 2 (or hydraulic motor 7) so that the fan rotation speed N of the cooling fan 8 becomes the abovementioned target fan rotation speed FANRPM. Note that the pressure oil of equipment 43 driven by drive source 1 is taken to include, inter alia, the pressure oil of a torque converter 43 and the hydraulic cylinders that drive the operating machinery.
With the third invention, a target fan rotation speed FANRPM that is necessary and sufficient for cooling is determined from the current temperature Tc of the cooling water and the temperature Ttc of the pressure oil, and the cooling fan 8 is rotated at this target fan rotation speed FANRPM.
Consequently, the cooling water and pressure oil are cooled with optimal energy efficiency. Also, the noise generated by the cooling fan itself is no greater than is necessary. That is, since the cooling fan rotation speed is varied without stages to the rotation speed necessary and sufficient for cooling, the cooling fan rotation speed does not exceed the rotation speed sufficient and necessary for cooling. Consequently, the rotation speed does not increase beyond the rotation speed necessary and sufficient for cooling and there are no energy losses. There is also no noise generated by the cooling fan. Furthermore, since there is no recirculation to the tank due to limiting the flow rate with a flow rate control valve, there are also no energy losses due to excessive flow rates.
Thus with the third invention, when driving a cooling fan with a hydraulic source, it is possible to drive it with optimal energy efficiency and to control noise to a minimum.
Furthermore, with the third invention, since the target fan rotation speed FANRPM that is necessary and sufficient for cooling is determined for the cooling water or the pressure oil, whichever of the cooling mediums, is insufficiently cool, and the cooling fan 8 is rotated at this target fan rotation speed FANRPM, it is possible to avoid situations where either the cooling water or pressure oil is insufficiently cooled, even when both are cooled by the cooling fan 8.
The fourth invention is a cooling fan drive control device according to the first, second or third invention, wherein:
it comprises a fan rotation speed sensing means 36 which senses the rotation speed of the cooling fan 8, and
the capacity control means 47, 40 controls the capacity 2a of the hydraulic pump 2 or the hydraulic motor 7 according to the difference between the target fan rotation speed set by the target fan rotation speed setting means 50 and the fan rotation speed sensed by the fan rotation speed sensing means 36.
The fourth invention is described with reference to FIGS. 1(a) and 1(b).
With the fourth invention, similar advantages are obtained as with the first, second and third inventions.
Furthermore, with the fourth invention, since the capacity 2a of the hydraulic pump 2 (or hydraulic motor 7) is controlled so as to eliminate the difference between the target fan rotation speed and the fan rotation speed sensed by the fan rotation speed sensing means 36, it is possible to make the fan rotation speed closely match the fan target rotation speed FANRPM. This further improves the energy efficiency. It also eliminates the occurrence of fluctuations in the controlled objectxe2x80x94i.e. the rotation speed of cooling fan 8xe2x80x94due to changes in the efficiency of hydraulic equipment such as the hydraulic pump 2 and the hydraulic motor 7 according to factors such as the pressure oil temperature.
The fifth invention is a cooling fan drive control device which comprises a hydraulic pump 2 driven by a drive source 1, a cooling fan 8 which cools cooling water of the drive source 1, and a hydraulic motor 7 which is operated by pressure oil discharged from the hydraulic pump 2 and causes the cooling fan 8 to rotate,
wherein it also comprises:
a capacity control means 47, 40 which controls a capacity 2a of the hydraulic pump 2 or the hydraulic motor 7 according to a difference between a temperature of the cooling water and a target temperature.
The fifth invention is described with reference to FIGS. 1(a) and 1(b) and FIG. 2.
With the fifth invention, the capacity 2a of the hydraulic pump 2 (or hydraulic motor 7) is controlled by the capacity control means (controller 47, EPC valve 40) so that the temperature of the cooling water reaches a target temperature.
With the fifth invention, the cooling fan 8 is rotated so that the cooling water reaches a target temperature. Consequently, the efficiency of engine 1 is always the optimal efficiency. And since there is no recirculation to the tank due to limiting the flow rate with a flow rate control valve, there are also no energy losses due to excessive flow rates.
In this way, with the fifth invention, the engine 1 can always be driven with optimal efficiency when the cooling fan is driven by a hydraulic source.
Furthermore, with the fifth invention, unlike the first invention, there is no need to determine a target fan rotation speed FANRPM for each cooling water temperature Tc. That is, there is no need to preset the relationship between each cooling water temperature Tc and each target fan rotation speed FANRPM for each type of equipment, and one need only determine a common cooling water target temperature for each type of equipment, allowing the work associated with setting computational formulae and/or memory tables to be performed easily.
The sixth invention is a cooling fan drive control device which comprises a hydraulic pump 2 driven by a drive source 1, a cooling fan 8 which cools pressure oil of equipment 43 operated by the drive source 1, and a hydraulic motor 7 which is operated by pressure oil discharged from the hydraulic pump 2 and causes the cooling fan 8 to rotate,
wherein it also comprises:
a capacity control means 47, 40 which controls a capacity 2a of the hydraulic pump 2 or the hydraulic motor 7 according to a difference between a temperature of the pressure oil and a target temperature.
The sixth invention is arrived at by substituting the cooling fan 8 which cools the cooling water in the fifth invention with a cooling fan 8 which cools the pressure oil.
With the sixth invention, similar advantages are obtained as with the fifth invention.
The seventh invention is a cooling fan drive control device according to the first, second or third invention, wherein:
the capacity control means 47, 40 performs control to gradually change the fan rotation speed of the cooling fan 8 until the fan rotation speed of the cooling fan 8 reaches the target fan rotation speed set by the target fan rotation speed setting means 50.
The seventh invention is described with reference to FIGS. 1(a) and 1(b).
With the seventh invention, similar advantages are obtained as with the first, second and third inventions.
Furthermore, with the seventh invention the fan rotation speed of cooling fan 8 is gradually changed until the fan rotation speed of cooling fan 8 reaches the target fan rotation speed FANRPM.
Consequently, sharp fluctuations in the fan rotation speed are prevented, and it is possible to prevent damage to the hydraulic equipment, especially the hydraulic motor 7.
The eighth invention is a cooling fan drive control device according to the first, second or third invention, wherein:
it comprises a compensation means 46 which, when the target fan rotation speed set by the target fan rotation speed setting means 50 is greater than or equal to a prescribed limiting rotation speed, compensates the target fan rotation speed to the limiting rotation speed, and
the capacity control means 47, 40 controls the capacity 2a of the hydraulic pump 2 or the hydraulic motor 7 according to the difference between the fan rotation speed of the cooling fan 8 and the compensated target fan rotation speed compensated by the compensation means 46.
The eighth invention is described with reference to FIGS. 1(a) and 1(b) and FIG. 2.
With the eighth invention, similar advantages are obtained as with the first, second and third inventions.
Also, with the eighth invention, when the target fan rotation speed (e.g. 1750 rpm) set by a target fan rotation speed setting means 50 is greater than or equal to a prescribed limiting rotation speed (e.g. 1225 rpm), the target fan rotation speed is compensated to this limiting rotation speed (1225 rpm), and the cooling fan 8 is rotated at this compensated target fan rotation speed (1225 rpm).
In this way, since the cooling fan 8 is rotated at a rotation speed not exceeding this prescribed limiting rotation speed, it is possible to suppress the noise to within a fixed level when noise is limited by regulations and the like, and further noise reductions can be achieved.
The ninth invention is a cooling fan drive control device according to first to eighth inventions, wherein:
it performs control to rotate the cooling fan 8 in an opposite rotation direction to a rotation direction when cooling the cooling water or the pressure oil at a prescribed time or at prescribed time intervals.
The ninth invention is described with reference to FIGS. 1(a) and 1(b).
With the ninth invention, similar advantages are obtained as with the first through eighth inventions.
Furthermore, with the ninth invention, cooling fan 8, which is provided opposite radiator 57 which dissipates heat from the cooling water or pressure oil, rotates in the opposite rotation direction to the rotation direction when cooling the cooling water or pressure oil at a prescribed time or at prescribed time intervals. Consequently, any dead leaves, dust or the like that have been sucked into the radiator 57 are periodically blown out. It is thereby possible to keep the interior of the chamber in which the radiator 57 is accommodated (the interior of the engine room) clean even when operating in environments where dead leaves, dust and the like are present in large quantities.
The tenth invention is a cooling fan drive control device according to the first through ninth inventions, wherein:
the capacity control means 47, 40 performs control to minimize the capacity 2a of the hydraulic pump 2 or the hydraulic motor 7 when the drive source 1 is started up.
The tenth invention is described with reference to FIGS. 1(a) and 1(b).
With the tenth invention, similar advantages are obtained as with the first through ninth inventions.
Furthermore, with the tenth invention, the capacity 2a of hydraulic pump 2 (or hydraulic motor 7) is minimized when the drive source (engine) 1 is started up, whereby sharp increases in oil pressure inside a hydraulic duct 42 can be suppressed. Also, since the load on the engine 1 is reduced, the starting properties of the engine 1 are improved.
The eleventh invention is a cooling fan drive control device according to the first through tenth inventions, wherein:
it performs control to increase the rotation speed of the cooling fan 8 to approximately a maximum rotation speed at prescribed time intervals.
The eleventh invention is described with reference to FIGS. 1(a) and 1(b).
With the eleventh invention, similar advantages are obtained as with the first through tenth inventions.
Also, with the eleventh invention, the rotation speed of cooling fan 8 is increased to approximately the maximum rotation speed at prescribed time intervals. This allows hot gases to be removed from the interior of the chamber in which the cooling fan 8 is accommodated the interior of the engine room, and it is thereby possible to improve the lifetime of components with relatively low heat resistance such as harnesses and hoses.
The twelfth invention is a cooling fan drive control device according to the first through eleventh inventions, wherein:
it comprises an indication means 55 that indicates the target fan rotation speed,
and the target fan rotation speed setting means 50 sets a target fan rotation speed corresponding to target fan rotation speed indication details indicated by the indication means 55.
The twelfth invention is described with reference to FIGS. 1(a) and 1(b).
With the twelfth invention, similar advantages are obtained as with the first through eleventh inventions.
Furthermore, with the twelfth invention, the target fan rotation speed FANRPM is set by taking into consideration not just the cooling water temperature and the pressure oil temperature, but also the target fan rotation speed indication details indicated by the indication means 55. Consequently, the rotation speed is controlled with greater detail, and it is possible to rotate the cooling fan 8 at a target rotation speed suited to the existing operating conditions, for example. In this way it is possible to further improve the energy efficiency.
The thirteenth invention is a cooling fan drive control device according to the first through twelfth inventions, wherein:
it comprises a hydraulic actuator 4 which is operated by pressure oil discharged from the hydraulic pump 2 being supplied via an operating valve 3, and a pump capacity control valve 20 which changes the capacity 2a of the hydraulic pump 2 so that a difference in pressure between a discharge pressure of the hydraulic pump 2 and a load pressure of the hydraulic actuator 4 becomes a desired set pressure difference.
The thirteenth invention is described with reference to FIG. 10.
With the thirteenth invention, similar advantages are obtained as with the first through twelfth inventions.
Furthermore, the hydraulic pump 2 of the thirteenth invention acts as a common hydraulic drive source for the hydraulic actuator 4 and the hydraulic motor 7 that drives the fan.
In a pump capacity control valve 20, load sensing control is performed to set the pressure difference between the discharge pressure P of the hydraulic pump 2 and the signal pressure corresponding to the load pressure PLS of the hydraulic actuator 4 to the desired pressure difference. Furthermore, the cooling fan 8 is rotated at a target fan rotation speed that is necessary and sufficient for cooling the cooling water or pressure oil by a capacity control means 13, 24 which controls the capacity 7c of the hydraulic motor 7. Alternatively, the efficiency of engine 1 or hydraulic cylinder 4 is maximized (optimized) by matching the temperature of the cooling water or pressure oil to a target temperature.
By performing this load sensing control and cooling fan rotation speed control (or temperature control) simultaneously, it is possible to increase the overall energy efficiency of the actuators of both the hydraulic actuator 4 and the hydraulic motor 7 used to drive the fan.